Efficient metal-insulator-metal capacitor fabrication

ABSTRACT

Methods of forming capacitors include forming a self-assembled pattern of periodic first and second domains using first and second block copolymer materials over a substrate. The second block copolymer material is etched away. Material from the substrate is etched based on a pattern defined by the first block copolymer material to form cavities in the substrate. A capacitor stack is conformally deposited over the substrate, such that the capacitor stack is formed on horizontal surfaces of the substrate and vertical surfaces of the cavities.

BACKGROUND Technical Field

The present invention generally relates to capacitor fabrication and,more particularly, to improved processes for fabricatingmetal-insulator-metal capacitors that use self-assembling blockcopolymers to increase capacitance per unit area without increasing thenumber of photomasks needed.

Description of the Related Art

Metal-insulator-metal capacitors are used throughout circuit designs toprovide integrated capacitors that can be formed during semiconductorfabrication processes instead of using discrete capacitors on circuitboard. However, to increase the capacitance per unit area, additionalsteps are needed to change the topography of the device. In particular,additional mask steps are often used to provide patterning. Theseadditional mask steps increase process complexity, and hence fabricationcosts, as well as potential plasma damage at the interface between metaland dielectric layers.

SUMMARY

A method for forming a capacitor includes forming a self-assembledpattern of periodic first and second domains using first and secondblock copolymer materials over a substrate. The second block copolymermaterial is etched away. Material from the substrate is etched based ona pattern defined by the first block copolymer material to form cavitiesin the substrate. A capacitor stack is conformally deposited over thesubstrate, such that the capacitor stack is formed on horizontalsurfaces of the substrate and vertical surfaces of the cavities.

A method for forming a capacitor includes forming a self-assembledpattern of periodic first and second domains using first and secondblock copolymer materials over a substrate. The second block copolymermaterial is etched away. A first mask is formed over the substrate.Material from the substrate is etched in an area exposed by the firstmask and the first block copolymer material to form cavities in thesubstrate. A capacitor stack is conformally deposited over thesubstrate, such that the capacitor stack is formed on horizontalsurfaces of the substrate and vertical surfaces of the cavities. Asecond mask is formed over the capacitor stack to define a capacitorarea. A same lithographic pattern and a developer of opposite polarityis used to form the second mask as is used to form the first mask. Thecapacitor stack is etched away from areas that are not covered by thesecond mask.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description will provide details of preferred embodimentswith reference to the following figures wherein:

FIG. 1 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 2 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 3 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 4 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 5 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 6 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 7 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 8 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 9 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 10 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 11 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 12 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 13 is a cross-sectional diagram of a step in the formation of ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention;

FIG. 14 is a block/flow diagram of a method of forming ametal-insulator-metal capacitor using block copolymers in accordancewith an embodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention use self-assembling blockcopolymers to define patterning regions before the deposition ofmetal-insulator-metal capacitor (MIMCAP) structures that make use of twometal layers with an insulator layer between them. Patterning creates amore complicated topography and increases the surface area of the MIMCAPstructures and, hence, the capacitance per unit area. The use of theself-assembling block copolymers removes the need for an extramasking/patterning step to define the patterning regions, therebydecreasing the process complexity.

Referring now to FIG. 1, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. Conductive contacts 104 areformed in an inter-layer dielectric 102. It should be understood that,while dielectric materials are particularly contemplated for theinterlayer dielectric 102, other substrate materials such as, e.g.,polymers, glass, resins, etc. may be used instead. It is specificallycontemplated that the interlayer dielectric 102 can be, e.g., silicondioxide, silicon nitride, or a low-k dielectric such as SiCOH. Theconductive contacts may be formed from any appropriate conductivematerial such as, e.g., tungsten, titanium, tantalum, ruthenium,zirconium, cobalt, copper, aluminum, lead, platinum, tin, silver, orgold.

A hardmask cap is formed from layers 106 and 108 over the interlayerdielectric 102 and the contacts 104. The layer 106 may be formed from anappropriate conductor cap to prevent oxidation of the contacts 104 andmay be formed from, e.g., tantalum nitride. The layer 106 may alsofunction as an etch stop layer in some cases. The layer 108 is ahardmask material such as, e.g., silicon nitride,tetraethylorthosilicate oxide, or any other appropriate hardmaskmaterial for later topography etching of the interlayer dielectric 102.

Referring now to FIG. 2, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. A neutral layer 202 is formedover the hardmask layer 108. A layer of self-assembling block copolymer(BCP) is formed over the neutral layer 202 by, e.g., a spin-coatingprocess. An exemplary BCP material is made of two linear and chemicallydistinct polymer chains covalently bonded together. BCPs canself-assemble into nanoscale structures having dimensions, pitch, andmorphology that are determined by the molecular weight of each block,the molecular weight of the BCP molecules, and the ratio of the twoblocks, respectively. In the present embodiments, a cylinder forming BCPsystem may be used, where the first block of the BCP forms matrix domain204 and the second block of BCP self-assemble in to the minority domain(cylinders) 206. At molecular level, the BCP chains, once annealed,organize themselves in contact with like materials, arranging themselvesabutting end-to-end. Thus, each microdomain is about the size of twoblocks. In one specific example, the self-assembling material may haveone block that is polystyrene, e.g., forming fins 204, and one blockthat is poly(methyl methacrylate) (PMMA), e.g., forming fins 206.

The neutral layer 202 modifies the surface energy and facilitates theself-assembled structures into vertical cylinders instead of in-planeparallel cylinders, which would have occurred if the substrate had astrong preference to one of the blocks of the BCP. The lengths of thepolymer chains can be selected to produce cylinders of diameter betweenabout 10 nm and about 100 nm. In this case, it is specificallycontemplated that the self-assembled cylinders may have acenter-to-center distance of about 20 nm to about 25 nm. An exemplaryannealing condition for self-assembly is a temperature between about200° C. to about 280° C. for a duration between about 2 minutes andabout 300 minutes under ambient atmosphere or a nitrogen atmosphere. Thearrangement of the resulting cylinders will be close to a hexagonalarray with local grain size ranging from tens to hundreds of nanometersdepending on the annealing conditions.

Referring now to FIG. 3, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. One of the self-assemblingmaterials is removed. For example, if polystyrene-PMMA BCPs are used,the PMMA block may be selectively etched with minimum damage to thepolystyrene. As used herein, the term “selective” in reference to amaterial removal process denotes that the rate of material removal for afirst material is greater than the rate of removal for at least anothermaterial of the structure to which the material removal process is beingapplied.

Referring now to FIG. 4, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. The pattern from theremaining polymer structure is transferred to the neutral layer 202 andhardmask layer 108, forming hardmask regions 402. The pattern can betransferred using, e.g., a directional etch such as reactive ion etching(RIE). The remaining polymer material from the first block ofself-assembling material 204 and the neutral layer 202 is etched away.

RIE is a form of plasma etching in which during etching the surface tobe etched is placed on the RF powered electrode. Moreover, during RIEthe surface to be etched takes on a potential that accelerates theetching species extracted from plasma toward the surface, in which thechemical etching reaction is taking place in the direction normal to thesurface. Other examples of anisotropic etching that can be used at thispoint of the present invention include ion beam etching, plasma etchingor laser ablation.

Referring now to FIG. 5, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. A first mask 502 is depositedto define a MIMCAP area 504. In one example, a layer of photoresistmaterial is deposited and is exposed over the MIMCAP area 504. Theexposed photoresist material can then be selectively removed. In analternative embodiment, regions outside the MIMCAP area 504 may beexposed, with the unexposed region being selectively removed.

Referring now to FIG. 6, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. The exposed regions of thecap layer 106 are anisotropically etched, exposing one of the conductivecontacts 104 and other regions of the interlayer dielectric 102. Exposedregions of the interlayer dielectric 102 are then anisotropically etchedto form cavities 602. The cavities 602 are used to provide topographiesthat will increase the capacitance of MIMCAPs.

It should be understood that an arbitrary number of cavities 602 may beformed to any appropriate depth. The cavities 602 are formed accordingto the exposed capacitor area 504, so a larger capacitor area 504 (asdefined by the mask 502) will result in more cavities. The horizontalarea of the cavities, meanwhile, is determined by the length of theblock copolymer chains, with longer chains producing larger blockstructures and, hence, larger cavities 602. The depth of the cavitiesmay be determined according to a timed etch, with a longer etchresulting in deeper cavities 602. It should be understood that the morecavities 602 are included, and the deeper those cavities 602 are, themore vertical surface is provided to increase the capacitance per unitarea of the ultimate MIMCAP.

Referring now to FIG. 7, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. The mask 502 is removed,followed by a wet clean to remove any residues or oxides that may remainon the exposed conductive material surfaces.

Referring now to FIG. 8, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. A first metal layer 802 isformed on the surface. The first metal layer 802 may be formed from anyappropriate conductive metallic material. It is specificallycontemplated that the first metal layer 802 may be formed from, e.g.,titanium nitride, although other materials may be used if they willreact with oxygen to form an insulating barrier layer. The first metallayer 802 may be formed by any appropriate process including, e.g.,chemical vapor deposition (CVD), physical vapor deposition (PVD), oratomic layer deposition (ALD).

CVD is a deposition process in which a deposited species is formed as aresult of chemical reaction between gaseous reactants at greater thanroom temperature (e.g., from about 25 ° C. about 900 ° C.). The solidproduct of the reaction is deposited on the surface on which a film,coating, or layer of the solid product is to be formed. Variations ofCVD processes include, but are not limited to, Atmospheric Pressure CVD(APCVD), Low Pressure CVD (LPCVD), Plasma Enhanced CVD (PECVD), andMetal-Organic CVD (MOCVD) and combinations thereof may also be employed.In alternative embodiments that use PVD, a sputtering apparatus mayinclude direct-current diode systems, radio frequency sputtering,magnetron sputtering, or ionized metal plasma sputtering. In alternativeembodiments that use ALD, chemical precursors react with the surface ofa material one at a time to deposit a thin film on the surface.

A dielectric layer 804 is deposited on the first metal layer 802 usingany appropriate process including, e.g., CVD, PVD, or ALD. Thedielectric layer 804 may be formed from any appropriate dielectricmaterial, but is specifically contemplated as being a high-k dielectricmaterial such as, e.g., hafnium dioxide, zirconium dioxide, aluminumoxide, tantalum oxide, and multilayers thereof. As used herein, the term“high-k” refers to a dielectric material having a dielectric constant kthat is higher than that of silicon dioxide.

A second metal layer 806 is deposited on top of the dielectric layer804. It is specifically contemplated that the second metal layer 806 maybe formed from, e.g., titanium nitride, although any other material maybe used instead. It is furthermore contemplated that the second metallayer 806 will be formed from the same material as the first metal layer802, although in some embodiments these two materials may differ. Thesecond metal layer 806 may be formed by any appropriate depositionprocess including, e.g., CVD, PVD, or ALD.

The first metal layer 802, dielectric layer 804, and second metal layer806 are formed conformally over the topography of the surface. Thisvertical extension effectively increases the capacitance of theresulting capacitor without increasing the horizontal surface areaconsumed by the device. Because capacitance for a capacitor generallyincreases with increased surface area between two conductive plates, thetopographical convolutions created by the cavities provide verticalsurfaces for capacitance in addition to the horizontal surfaces.

Referring now to FIG. 9, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. A protective layer 904 isformed on the capacitor area and a mask 902 is formed over theprotective 904. In this case the same mask and material may be used aswas used for the first mask 502, but a developer of the opposite tonemay be used (e.g., removing the unexposed region where the exposedregion was removed in FIG. 5, or removing the exposed region if theunexposed region was removed in FIG. 5). The result is that the mask 902is in the same location as the open capacitor area 504 formed by thefirst mask 502.

The protective layer 904 protects the underlying portions of the MIMstack from damage during the definition of the mask 902 and thesubsequent etching of the MIM stack outside of the area protected by themask 902. Thus the protective layer 904 may be any appropriate materialthat has etch selectivity with respect to the mask 902 and the secondmetal layer 806.

Referring now to FIG. 10, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. The first metal layer 802,dielectric layer 804, and second metal layer 806 are etched away in theareas around the second mask 902, leaving behind MIMCAP 1002. Anyappropriate anisotropic etch or combination of etches may be used toremove this material, said etches selectively removing the metal anddielectric layers without affecting the hardmask regions 402 or theunderlying cap layer 106.

Referring now to FIG. 11, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. The mask 902 is removed,leaving the hardmask 904 over the MIMCAP 1002.

Referring now to FIG. 12, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. After the exposed surfacesare cleaned using, e.g., a wet clean, a layer of dielectric material1202 is deposited over the MIMCAP 1002 and surrounding structures. Thelayer of dielectric material 1202 may be, e.g., a low-k dielectricmaterial and may be the same material as the interlayer dielectric 102.Any appropriate deposition process may be used to form the layer ofdielectric material 1202 including, e.g., CVD, ALD, or PVD.

Once the layer of dielectric material 1202 is deposited, the top surfacemay be planarized using, e.g., chemical mechanical planarization (CMP).CMP is performed using, e.g., a chemical or granular slurry andmechanical force to gradually remove upper layers of the device. Theslurry may be formulated to be unable to dissolve, for example, the workfunction metal layer material, resulting in the CMP process's inabilityto proceed any farther than that layer.

Referring now to FIG. 13, a cross-sectional diagram of a step in thefabrication of MIMCAP structures is shown. A new mask is used to patternan opening in the layer of dielectric material 1202 and a contact 1302is formed therein. The contact 1302 may be formed from any appropriateconductive material and may, in particular, be formed from the samematerial as the conductive contacts 104. It should be understood thattwo masks are therefore used—a first mask that is used twice two definethe capacitor area and a second mask that is used to define the topcontact 1302. No additional material is needed to change the topographythat is provided by the cavities 602.

It is to be understood that aspects of the present invention will bedescribed in terms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps can be varied within the scope of aspects of the presentinvention.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements can also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements can be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

The present embodiments can include a design for an integrated circuitchip, which can be created in a graphical computer programming language,and stored in a computer storage medium (such as a disk, tape, physicalhard drive, or virtual hard drive such as in a storage access network).If the designer does not fabricate chips or the photolithographic masksused to fabricate chips, the designer can transmit the resulting designby physical means (e.g., by providing a copy of the storage mediumstoring the design) or electronically (e.g., through the Internet) tosuch entities, directly or indirectly. The stored design is thenconverted into the appropriate format (e.g., GDSII) for the fabricationof photolithographic masks, which typically include multiple copies ofthe chip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein can be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case, the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case, the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

It should also be understood that material compounds will be describedin terms of listed elements, e.g., SiGe. These compounds includedifferent proportions of the elements within the compound, e.g., SiGeincludes Si_(x)Ge_(1-x) where x is less than or equal to 1, etc. Inaddition, other elements can be included in the compound and stillfunction in accordance with the present principles. The compounds withadditional elements will be referred to herein as alloys.

Reference in the specification to “one embodiment” or “an embodiment”,as well as other variations thereof, means that a particular feature,structure, characteristic, and so forth described in connection with theembodiment is included in at least one embodiment. Thus, the appearancesof the phrase “in one embodiment” or “in an embodiment”, as well anyother variations, appearing in various places throughout thespecification are not necessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This can be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, can be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the FIGS. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the FIGS. For example, if the device in theFIGS. is turned over, elements described as “below” or “beneath” otherelements or features could then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device can be otherwise oriented (rotated 90degrees or at other orientations and the spatially relative descriptorsused herein can be interpreted accordingly. In addition, it will also beunderstood that when a layer is referred to as being “between” twolayers, it can be the only layer between the two layers, or one or moreintervening layers can also be present.

It will be understood that, although the terms first, second, etc. canbe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. Thus, a first element discussed belowcould be termed a second element without departing from the scope of thepresent concept.

Referring now to FIG. 14, a method of forming a MIMCAP is shown. Block1402 forms self-assembled nanoscale domains 204 and 206 over a hardmasklayer 108 which, in turn, lies over a dielectric layer 102 withconductive contacts 104 embedded therein. The self-assembled domains 204and 206 are formed by block copolymer chains having two blocks on eachchain that comprise distinct chemical compositions. Upon annealing, theBCP molecules rearrange where like ends of different molecules form ingroups, resulting in periodic structures.

Block 1404 etches away one of the copolymer materials. In particular,minority domain 206 is etched away, leaving the other material in place.Block 1405 transfers the resulting pattern to hardmask layer 108 to formhardmask regions 402. The transfer of the pattern may be performed usingan anisotropic etch that selectively removes material from the hardmasklayer 108.

Block 1406 forms mask 502 that defines capacitor area 504. Block 1408transfers the pattern in the exposed capacitor area 504 down into thedielectric layer 102, exposing at least one conductive contact 104 andcreating cavities 602. Block 1410 removes the mask 502.

Block 1412 forms the MIMCAP capacitor stack, including a first metallayer 802, a dielectric layer 804, and a second metal layer 806. Thecapacitor stack is formed without patterning steps between layers,thereby minimizing plasma damage on the interfaces and improving deviceyield.

Block 1414 forms mask 902 over the capacitor area 504, for example usingthe same lithographic mask as was used in block 1406 but with adeveloper of an opposite polarity. Block 1416 anisotropically etchesaway the layers of the capacitor stack outside of the capacitor area504. Block 1418 removes the mask 902. After the capacitor 1002 isformed, block 1420 deposits a layer of dielectric material 1202. Thelayer of dielectric material 1202 may be deposited by any appropriateprocess such as, e.g., CVD, ALD, or PVD, and then planarized using,e.g., CMP. Block 1422 forms an opening in the layer of dielectricmaterial 1202 and hardmask 904 using, e.g., an appropriate mask and ananisotropic etch. Block 1422 then forms top contact 1302 in the openingto complete the capacitor.

Having described preferred embodiments of a system and method (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations can be made by persons skilled in the artin light of the above teachings. It is therefore to be understood thatchanges may be made in the particular embodiments disclosed which arewithin the scope of the invention as outlined by the appended claims.Having thus described aspects of the invention, with the details andparticularity required by the patent laws, what is claimed and desiredprotected by Letters Patent is set forth in the appended claims.

What is claimed is:
 1. A method for forming a capacitor, comprising:forming a self-assembled pattern of periodic first and second domainsusing first and second block copolymer materials over a substrate;etching away the second block copolymer material; etching material fromthe substrate based on a pattern defined by the first block copolymermaterial to form cavities in the substrate; and conformally depositing acapacitor stack over the substrate, such that the capacitor stack isformed on horizontal surfaces of the substrate and vertical surfaces ofthe cavities.
 2. The method of claim 1, further comprising forming amask over the capacitor stack to define a capacitor area and etchingaway the capacitor stack from areas that are not covered by the mask. 3.The method of claim 2, further comprising forming a mask over thesubstrate before etching material from the substrate to limit an etchedarea.
 4. The method of claim 3, wherein forming the mask over thecapacitor stack and forming the mask over the substrate compriselithographically defining the respective masks using a same lithographicpattern and developers of opposite polarity.
 5. The method of claim 1,further comprising depositing a layer of dielectric material over thecapacitor stack.
 6. The method of claim 5, forming a top conductivecontact through the layer of dielectric material to contact thecapacitor stack.
 7. The method of claim 6, wherein conformallydepositing the capacitor stack comprises depositing the capacitor stackin contact with a bottom conductive contact that is embedded in thesubstrate.
 8. The method of claim 1, wherein the first block copolymermaterial is polystyrene and the second block copolymer material ispoly(methyl methacrylate).
 9. A method for forming a capacitor,comprising: forming a self-assembled pattern of periodic first andsecond domains using first and second block copolymer materials over asubstrate; etching away the second block copolymer material; forming afirst mask over the substrate; etching material from the substrate in anarea exposed by the first mask and the first block copolymer material toform cavities in the substrate; conformally depositing a capacitor stackover the substrate, such that the capacitor stack is formed onhorizontal surfaces of the substrate and vertical surfaces of thecavities; forming a second mask over the capacitor stack to define acapacitor area, wherein a same lithographic pattern and a developer ofopposite polarity is used to form the second mask as is used to form thefirst mask; and etching away the capacitor stack from areas that are notcovered by the second mask.
 10. The method of claim 9, furthercomprising depositing a protective layer over the capacitor stack beforeforming the second mask.
 11. The method of claim 9, further comprisingdepositing a layer of dielectric material over the capacitor stack. 12.The method of claim 11, forming a top conductive contact through thelayer of dielectric material to contact the capacitor stack.
 13. Themethod of claim 12, wherein conformally depositing the capacitor stackcomprises depositing the capacitor stack in contact with a bottomconductive contact that is embedded in the substrate.
 14. The method ofclaim 9, wherein the first block copolymer material is polystyrene andthe second block copolymer material is poly(methyl methacrylate).